1. Field of the Invention
The present invention relates generally to pulsed alternator current sources, and, more particularly, the present invention is directed to systems and methods for utilizing multiple pairs of pulsed alternators with an interleaved pulse control mechanism to drive large electromagnetic launcher loads.
2. Description of the Background
It is well known in the art that specialized rotating generators can be used to store kinetic energy and convert it to high current electrical energy in the millisecond time frame. Such generators, called pulsed alternators can be used to drive electromagnetic launcher loads that are used to propel a projectile or other object along an intended path. One application of these launchers is for high-energy electromagnetic launchers in the form of “rail guns.” These rail guns use a pulsed power system to launch a projectile very long distances with a high degree of accuracy and are especially suited for mobile design (onboard a ship or mobile gun turret).
The pulsed alternator's high degree of rotating stored energy and extreme torques generated during discharge mandate that a torque and inertia management scheme be employed to control the reaction transmitted to the system base structure. To address the high torque of these large machines, pairs of pulsed alternators with contra-rotating rotors are used to mitigate the reaction torque effects. By spinning in opposite directions, the torque from each pulsed alternator tends to cancel each other and the total torque on the system base structure approaches a negligible value.
Therefore, when used as pulsed power sources, pulsed alternator systems are configured with single or multiples pairs of contra-rotating machines (generators). The more pairs of machines that are used, the higher the amount of energy that can be stored and subsequently released. For high-energy applications such as a rail gun, several pairs of pulsed alternators may be needed. The present invention is most pertinent to pulsed power sources in which multiple pairs of pulsed alternators are utilized.
In multiple alternator systems, each of the pulsed alternators is characterized by an AC (alternating current) output. In conventional pulsed alternator systems, the AC generator outputs are rectified with identical gating pulses sent to the rectifier switches for each rotating machine. Such an identical gating scheme causes each of the pulsed alternators to be in phase. Therefore, the current pulses from each machine add together in phase to produce a DC (direct current) current pulse. Likewise, in conventional systems with multiple pairs of pulsed alternators, all rectifier switches for each output are identically controlled, and current from all the machines would be added together in phase. While such a gating scheme allows all of the output current from each of the alternators to be added together for the highest possible output current, it also produces a typical load current pulse with a “ripple” as shown in FIG. 1.
Ideally, the high-energy electromagnetic launcher load requires a smooth DC current pulse with as little ripple as possible (e.g., a square wave). Pulsed power sources including multiple pairs of pulsed alternators that can reduce or eliminate this unwanted ripple are continually sought in the art. The present invention, through its disclosed embodiments, addresses one or more of the above-described limitations of the prior art to provide a pulsed power source with improved output current characteristics.